Magnetorheological fluid clutch apparatus and control systems

ABSTRACT

A magnetorheological fluid clutch apparatus comprises an input rotor adapted to be coupled to a power input, the input rotor having a first set of at least one input shear surface, and a second set of at least one output shear surface. An output rotor is rotatably mounted about the input rotor for rotating about a common axis with the input rotor, the output rotor having a first set of at least one output shear surface, and a second set of at least one output shear surface, the first sets of the input rotor and the output rotor separated by at least a first annular space and forming a first transmission set, the second sets of the input rotor and the output rotor separated by at least a second annular space and forming a second transmission set. Magnetorheological fluid is in each of the annular spaces, the MR fluid configured to generate a variable amount of torque transmission between the sets of input rotor and output rotor when subjected to a magnetic field. A pair of electromagnets are configured to deliver a magnetic field through the MR fluid, the electromagnets configured to vary the strength of the magnetic field, whereby actuation of at least one of the pair of electromagnets results in torque transmission from the at least one input rotor to the output rotor.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority on U.S. Patent Application No.61/934,141, filed on Jan. 31, 2014.

TECHNICAL FIELD

This invention relates generally to magnetorheological (MR) fluid clutchapparatuses, and more particularly, to configurations of such apparatusfor various applications.

BACKGROUND

Magnetorheological (MR) fluid clutch apparatuses are known as usefulapparatuses for transmitting motion from a drive shaft with precisionand accuracy, among other advantages. Accordingly, an increasing numberof applications consider the use of MR fluid clutch apparatuses. Forthis purpose, it is desirable to modify existing MR fluid clutchapparatuses to bring them to safety standards of their givenapplications, for instance in terms of redundancy.

SUMMARY

It is an aim of the present disclosure to provide magnetorheological(MR) fluid clutch apparatuses that addresses issues associated with theprior art.

It is a further aim of the present disclosure to provide novel controlsystems with magnetorheological (MR) fluid clutch apparatuses.

Therefore, in accordance with a first embodiment of the presentdisclosure, there is provided a magnetorheological fluid clutchapparatus comprising: at least one input rotor adapted to be coupled toa power input, the input rotor having a first set of at least one inputshear surface, and a second set of at least one output shear surface; anoutput rotor rotatably mounted about the input rotor for rotating abouta common axis with the input rotor, the output rotor having a first setof at least one output shear surface, and a second set of at least oneoutput shear surface, the first sets of the input rotor and the outputrotor separated by at least a first annular space and forming a firsttransmission set, the second sets of the input rotor and the outputrotor separated by at least a second annular space and forming a secondtransmission set; magnetorheological fluid in each of the annularspaces, the MR fluid configured to generate a variable amount of torquetransmission between the sets of input rotor and output rotor whensubjected to a magnetic field; and a pair of electromagnets, with afirst electromagnet associated with the first transmission set, and asecond electromagnet associated with the second transmission set, theelectromagnets configured to deliver a magnetic field through the MRfluid, the electromagnets configured to vary the strength of themagnetic field; whereby actuation of at least one of the pair ofelectromagnets results in torque transmission from the at least oneinput rotor to the output rotor.

Further in accordance with the first embodiment, each of the first setof input shear surface and the second set of input shear surfaces arepart of first input drums and second input drums, and further wherein atleast one of each of the output shear surfaces are part of first outputdrums and second output drums, the input and output shear surfaces ofeach of the transmission sets being intertwined.

Still further in accordance with the first embodiment, the at leastfirst annular space is part of a first magnetorheological fluid chamber,and further wherein the at least second annular space is part of asecond magnetorheological fluid chamber.

Still further in accordance with the first embodiment, each of themagnetorheological fluid chambers has an expansion system.

Still further in accordance with the first embodiment, the expansionsystem comprises at least one flexible member on an exterior of theoutput rotor forming an expansion pocket in fluid communication with oneof the magnetorheological fluid chambers.

Still further in accordance with the first embodiment, each of theelectromagnets comprises at least two independent coils.

Still further in accordance with the first embodiment, one of the inputdrums and the output drums has a helical channel in at least one of itssurfaces facing the annular space, the annular space being in fluidcommunication with a fluid chamber space, whereby the helical channelinduces a flow of the magnetorheological fluid between the annular spaceand the fluid chamber space when the input rotor rotates.

Still further in accordance with the first embodiment, the fluid chamberspace is separated from the annular space by at least one hole in aradial wall of the input drums.

Still further in accordance with the first embodiment, the at least oneinput rotor comprises two input rotors, with a first of the input rotorsassociated with the first transmission set and a second of the inputrotors associated with the second transmission set.

Still further in accordance with the first embodiment, the first of theinput rotors receives a clockwise input, and further wherein the secondof the input rotors receives a counterclockwise input.

Still further in accordance with the first embodiment, the first of theinput rotors receives a rotating input, and further wherein the secondof the input rotors is fixed.

Still further in accordance with the first embodiment, the pair ofelectromagnets share a common core, the common core being fixed to theoutput rotor.

In accordance with a second embodiment of the present disclosure, thereis provided a magnetorheological fluid clutch apparatus comprising: atleast one input rotor adapted to be coupled to a power input, the inputrotor having at least a first set of at least one input drum; an outputrotor rotatably mounted about the input rotor for rotating about acommon axis with the input rotor, the output rotor having at least afirst set of at least one output shear surface, the first sets of theinput rotor and the output rotor separated by at least a first annularspace and forming a first transmission set; a fluid chamber space beingin fluid communication with the annular space, at least one surfacedepression channel in a surface of one of the at least one input drumand the at least one output shear surface facing the annular space;magnetorheological fluid in the annular space, the MR fluid configuredto generate a variable amount of torque transmission between the sets ofinput rotor and output rotor when subjected to a magnetic field; and atleast one electromagnet configured to deliver a magnetic field throughthe MR fluid, the at least one electromagnet configured to vary thestrength of the magnetic field whereby actuation of the at least oneelectromagnets resulting in torque transmission from the at least oneinput rotor to the output rotor; whereby the surface depression inducesa flow of the magnetorheological fluid between the annular space and thefluid chamber space when the input rotor rotates.

Further in accordance with the second embodiment, each of the first setof at least one input drums comprises a plurality of the input drums,and wherein at least one of the output shear surfaces is part of a firstoutput drum, the input drum and output shear surfaces being intertwined.

Still further in accordance with the second embodiment, the at leastfirst annular space is part of a first magnetorheological fluid chamber.

Still further in accordance with the second embodiment, wherein themagnetorheological fluid chamber has an expansion system.

Still further in accordance with the second embodiment, the expansionsystem comprises at least one flexible member on an exterior of theoutput rotor forming an expansion pocket in fluid communication with themagnetorheological fluid chamber.

Still further in accordance with the second embodiment, the at least oneelectromagnet comprises at least two independent coils.

Still further in accordance with the second embodiment, the at least oneinput rotor receives an axial power input, and the output rotor has oneof an axially-positioned connector and a radial connector fortransmitting a power output.

Still further in accordance with the second embodiment, the at least oneinput rotor comprises two input rotors, with a first of the input rotorsassociated with the first transmission set and a second of the inputrotors associated with a second transmission set.

Still further in accordance with the second embodiment, the first of theinput rotors receives a rotating input, and further wherein the secondof the input rotors is fixed.

Still further in accordance with the second embodiment, the at least onesurface depression is at least one helical channel.

In accordance with a third embodiment of the present disclosure, thereis provided an actuation system comprising: four power sources eachproducing one degree of rotational power; a first power shaft connectedto two of the power sources for receiving the degrees of rotationalpower for rotating in a first orientation, with one of the two degreesof rotational power being redundant; a second power shaft connected totwo other of the power sources for receiving the degrees of rotationalpower in a second orientation opposite to the first orientation, withone of the two degrees of rotational power being redundant; at least onemagnetorheological fluid clutch apparatus on the first power shaft andactuatable to output at least partially rotational power in the firstorientation received from the first power shaft; at least onemagnetorheological fluid clutch apparatus on the second power shaft andactuatable to output at least partially rotational power in the secondorientation received from the second power shaft; and at least onelinkage connected to the magnetorheological fluid clutch apparatuses onthe first power shaft and on the second power shaft to movereciprocatingly upon actuation of the magnetorheological fluid clutchapparatuses.

Further in accordance with the third embodiment, a plurality of themagnetorheological fluid clutch apparatuses are on the first power shaftand on the second power shaft, with pairs of one magnetorheologicalfluid clutch apparatus on the first power shaft and onemagnetorheological fluid clutch apparatus on the second power shaftbeing formed and interconnected by a respective one of the linkages.

Still further in accordance with the third embodiment, unidirectionalclutches are provided between each of the power sources and a respectiveone of the power shafts.

Still further in accordance with the third embodiment, right-anglegearboxes are between each of the power sources and a respective one ofthe power shafts.

Still further in accordance with the third embodiment, the four powersources are produced by two motors, each motor having two drive shafts.

Still further in accordance with the third embodiment, the four powersources are produced by four motors.

In accordance with a fourth embodiment of the present disclosure, thereis provided an actuation system comprising: at least one power sourceproducing one degree of rotational power; a power shaft connected to thepower source for receiving the degree of rotational power for rotatingin a first orientation; at least a pair of magnetorheological fluidclutch apparatuses on the power shaft and each actuatable to output atleast partially rotational power received from the power shaft via anoutput arm; and at least one linkage having an output end, a firstsublinkage extending from the output end to a first joint with theoutput arm of one of the magnetorheological fluid clutch apparatuses ofthe pair, a second sublinkage extending from the output end to a secondjoint with the output arm of the other of the magnetorheological fluidclutch apparatuses of the pair, the first joint and the second jointbeing on opposite sides of a plane passing through an axis of the powershaft and the output end; whereby the output end moves reciprocatinglyupon actuation of the magnetorheological fluid clutch apparatuses.

Further in accordance with the fourth embodiment, a plurality of pairsof magnetorheological fluid clutch apparatuses are provided, each saidpair having one linkage, the pairs sharing the power shaft.

Still further in accordance with the fourth embodiment, the power sourceis a single motor.

In accordance with a fifth embodiment of the present disclosure, thereis provided an actuation system comprising: two rotary units, eachrotary unit comprising: a power source producing one degree ofrotational power; a magnetorheological fluid clutch apparatus receivingthe rotational power from the power source and actuatable to output atleast partially rotational power received from the power source; and atleast a shared output arm connected to the magnetorheological fluidclutch apparatus of both of the rotary units, the shared output armmoving upon actuation of either or both of the magnetorheological fluidclutch apparatuses.

Further in accordance with the fifth embodiment, a gearbox is in each ofthe rotary units between the power source and the magnetorheologicalfluid clutch apparatus.

Still further in accordance with the fifth embodiment, one of the rotaryunits causes a clockwise movement of the shared output arm, and theother of the rotary units causes a counterclockwise movement of theshared output arm.

Still further in accordance with the fifth embodiment, the power sourcesof each said rotary unit is a bidirectional power source.

In accordance with a sixth embodiment of the present disclosure, thereis provided an actuation system comprising: at least two independentrotary units, each rotary unit comprising a power source producing onedegree of rotational power; a magnetorheological fluid clutch apparatusreceiving the rotational power from the power source and actuatable tooutput at least partially rotational power received from the powersource; a linkage connected to the magnetorheological fluid clutchapparatus to receive the output; and a shared rotary unit comprising: ashared power source producing one degree of rotational power; a powershaft receiving the rotational power from the shared power source; amagnetorheological fluid clutch apparatus for each of the at least twoindependent rotary units, and receiving the rotational power from theshared power source and actuatable to output at least partiallyrotational power received from the shared power source; wherein thelinkages of each of the at least two independent rotary units isconnected to a dedicated one of the magnetorheological fluid clutchapparatus of the shared rotary unit to receive rotational power from theshared rotary unit.

Further in accordance with the sixth embodiment, a gearbox is in each ofthe rotary units between the power source and the magnetorheologicalfluid clutch apparatus.

Still further in accordance with the sixth embodiment, one ofindependent rotary units produce a clockwise rotation, and the sharedrotary unit produces a counterclockwise rotation.

Still further in accordance with the sixth embodiment, the independentrotary units and the shared rotary unit all produce rotation in a commonorientation, with the degree of rotational power of the shared rotaryunit being redundant.

Still further in accordance with the sixth embodiment, the power sourceof at least one said rotary unit is a bidirectional power source.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A shows a principle of operation of a magnetorheological (MR)fluid clutch apparatus according to one example embodiment, without amagnetic field;

FIG. 1B shows the MR fluid clutch apparatus of FIG. 1A when subject to asuitable magnetic field;

FIG. 2A shows a perspective view of a MR fluid clutch apparatus inaccordance with an embodiment of the present disclosure, for axial inputand output for axial shaft;

FIG. 2B is a sectioned perspective view of an input rotor of the MRfluid clutch apparatus of FIG. 2A;

FIG. 2C is an enlarged perspective view of a helical channel for drum ofthe input rotor of FIG. 2B;

FIG. 2D is a sectioned perspective view of an output rotor of the MRfluid clutch apparatus of FIG. 2A;

FIG. 2E is a sectioned assembly view of an output casing of the outputrotor of FIG. 2D FIG. 2F is an enlarged cross-section view of the MRfluid clutch apparatus of FIG. 2A; FIG. 2G is further enlarged view ofthe cross-section view of FIG. 2F, focusing on drum interrelation;

FIGS. 2H and 2I show example magnetic fields of the MR fluid clutchapparatus of FIGS. 2A-2G;

FIG. 2J is a sectioned view of the MR fluid clutch apparatus of FIGS.2A-2G, showing a MR fluid flow;

FIG. 3 is an MR fluid clutch apparatus in accordance with anotherembodiment of the present disclosure, with two independent axial inputsfor a radial connector on the output;

FIG. 4A is a schematic top view of a controlled-slippage actuation (CSA)system that incorporates MR fluid clutch apparatuses such as the MRfluid clutch apparatus of FIGS. 2A-2D;

FIG. 4B is a perspective view of the CSA system of FIG. 4A;

FIG. 5 is an alternative embodiment of a CSA system that incorporates MRfluid clutch apparatuses such as the MR fluid clutch apparatus of FIGS.2A-2D;

FIG. 6 is a perspective view of a clutch-redundant rotary motor (CRRM)system that incorporates MR fluid clutch apparatuses such as the MRfluid clutch apparatus of FIGS. 2A-2D; and

FIG. 7 is a schematic top view of an alternative embodiment of a CRRMsystem that incorporates MR fluid clutch apparatuses such as the MRfluid clutch apparatus of FIGS. 2A-2D.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to the drawings and more particularly to FIGS. 1A and 1B,there is illustrated the principle of operation of a magnetorheological(MR) fluid clutch apparatus 10 configured to provide a mechanical outputforce based on a received input current.

As will be explained in greater detail below and in variousconfigurations, a MR fluid clutch apparatus 10 may provide an outputforce in response to an input current received from an operator, totransmit an input force. For example, FIGS. 1A and 1B show exampleconceptual views of a MR fluid clutch apparatus 10 according to oneexample embodiment. The example MR fluid clutch apparatus 10 featuresdriving member 12 and driven member 14 separated by gaps filled with anMR fluid 16. In the example of FIGS. 1A and 1B, the driving member 12may be in mechanical communication with a power input, and driven member14 may be in mechanical communication with a power output (i.e., forceoutput, torque output).MR fluid 16 is a type of smart fluid that iscomposed of magnetisable particles disposed in a carrier fluid, usuallya type of oil. When subjected to a magnetic field, the fluid mayincrease its apparent viscosity, potentially to the point of becoming aviscoplastic solid. The apparent viscosity is defined by the ratiobetween the operating shear stress and the operating shear rate of theMR fluid comprised between opposite shear surfaces. The magnetic fieldintensity mainly affects the yield shear stress of the MR fluid. Theyield shear stress of the fluid when in its active (“on”) state may becontrolled by varying the magnetic field intensity produced byelectromagnets (not shown in FIGS. 1A and 1B), i.e., the input current,via the use of a controller. Accordingly, the MR fluid's ability totransmit force can be controlled with an electromagnet, thereby actingas a clutch between the members 12 and 14. The electromagnet unit isconfigured to vary the strength of the magnetic field such that thefriction between the members 12 and 14 is low enough to allow thedriving member 12 to freely rotate with the driven member 14 and viceversa.

FIG. 1A shows MR fluid clutch apparatus 10 when the MR fluid 16 issubject to little or no magnetic flux, whereas FIG. 1B shows MR fluidclutch apparatus 10 when the MR fluid 16 is subject to a larger magneticflux. Accordingly, the example of FIG. 1A may allow relativelyindependent movement between members 12 and 14, whereas the example ofFIG. 1B may restrict movement between members 12 and 14. Accordingly, MRfluid clutch apparatus 10 may vary the amount of force provided inresponse to a received input by changing the amount of magnetic flux towhich is exposed the MR fluid 16. In particular, the MR fluid clutchapparatus 10 may provide an output force based on the input force bychanging the amount of magnetic flux based on the input force. Inaddition, the MR fluid clutch apparatus 10 may be less prone tocomponent failures than some other clutches because MR fluid 16 mayinvolve lower friction between members 12 and 14 than conventionalclutches.

FIGS. 2A to 2J show an embodiment of the MR fluid clutch apparatus at10′, providing additional detail over the system 10 of FIGS. 1A and 1B.FIG. 2A shows a perspective view of the MR fluid clutch apparatus 10′.FIGS. 2B and 2C show the driving member 12, while FIGS. 2D and 2E showthe driven member 14 separate from one another. FIG. 2F shows across-section view of the MR fluid clutch apparatus 10′ of FIG. 2A. FIG.2G shows a detailed view of the cross section view of FIG. 2F.

The MR fluid clutch apparatus 10′ features the driving member 12, thedriven member 14, and an electromagnet unit 18 that is secured to thedriven member 14, with MR fluid 16 disposed between the driving member12 and the driven member 14. In the example of FIGS. 2A-2J, the drivingmember 12 is represented by an input rotor having a hub 20, by which thedriving member 12 may be connected to a shaft or like rotational powerinput. Therefore, the driving member 12 may receive rotational energy(torque) from a power device, such as a motor. The driving member 12further comprises an annular rim 21, supported radially about the hub 20by way of spokes 22. This is one possible configuration, as the annularrim 21 may be connected to the hub 20 by way of a disc, or otherarrangements. The driving member 12 rotates about axis CL.

A pair of flanges 23A and 23B (a.k.a., radial walls) project radiallyfrom the rim 21, although a single one of the flanges 23 couldalternatively be present. The flanges 23A and 23B each has a pluralityof concentric annular drums 24A or 24B, respectively. In the embodimentof FIGS. 2A to 2D, the flanges 23A and 23B are arranged to have theirrespective sets of annular drums 24A-B face each other, although otherarrangements are considered as well. The annular drums 24A-B are securedto the flanges 23A-B. In an embodiment, concentric circular channels aredefined (e.g., machined, cast, molded, etc) in the flanges 23A and 23Bfor insertion therein of the drums 24A/24B. A tight fit (e.g., forcefit), an adhesive and/or radial pins may be used to secure the drums24A/24B in their respective flanges 23A-23B. In the illustratedembodiment, the flanges 23A-B are monolithically connected to the hub20, the annular rim 21 and the spokes 22, whereby the various componentsof the driving member 12 rotate concurrently when receiving the drivefrom the power source.

As shown in FIG. 2C, a helical channel 25 may be defined in one or moreof the surfaces of the drums 24A and 24B. The channel 25 is said to behelical in that it has a varying axial dimension when one moves alongthe channel 25. The helical channel 25 constitutes a path for the MRfluid. Indeed, the channels 25 in the set of drums 24A and 24B causes apumping action of the MR fluid 16 in the MR fluid chambers. Thus, animportant portion of the MR fluid in the MR fluid chambers participatesin the transmission of the torque, which helps to increase the life ofthe MR fluid clutch apparatus 10′. The channels are right-handed (orleft-handed) on both annular surfaces of each drum comprised in the setof drums 24A and 24B. Some holes 26 (FIG. 2B) are present in the annularflanges 23A and 23B so that the internal MR fluid flow is possible, asexplained hereinafter.

Various bearings 30 are mounted to the driving member 12 and rotatablysupport the driven member 14, such that the driven member 14 may rotatewhen the clutch apparatus 10 is actuated to transmit the rotationalmovement, as described hereinafter. Seals 31 are also provided at theinterface between the driving member 12 and driven member 14, topreserve the MR fluid 16 between the members 12 and 14. Moreover, theseals 31 are provided to prevent MR fluid from reaching the bearings 30or to leak out of the apparatus 10′.

Also in this example, the driven member 14 is represented by an outputcasing 40, also referred to as output rotor, configured to rotate aboutaxis CL as well. The output casing 40 may be coupled to variousmechanical components that receive the transmitted power output when theclutch apparatus 10′ is actuated to transmit at least some of therotational power input. The output casing 40 has a first annular half40A and a second annular half 40B, interconnected by respective flanges41A and 41B and fasteners 42. A hub 43 is fixed to the second annularhalf 40B, so as to rotate with it. The driven member 14 is connected tomechanical components via the hub 43, whereby fasteners 43A are providedto couple the hub 43 to such mechanical components (not shown).

The driven member 14 also has a pair of sets of concentric annular drums44A or 44B, respectively mounted to annular supports 45A and 45B,respectively. The annular supports 45A and 45B are secured to a core ofelectromagnet unit 18 as is described hereinafter (e.g., by press-fit,glue, dowel, etc). The annular drums 44A and 44B are spaced apart insuch a way that the sets of annular drums 24A and 24B fit within theannular spaces between the annular drums 44A and 44B, in intertwinedfashion. When either of both the driving member 12 and the driven member14 rotate, there is no direct contact between the annular drums 24A and24B, and the annular drums 44A and 44B, due to the concentricity of theannular drums 24A, 24B, 44A and 44B, about axis CL.

The annular spaces between the annular drums 24A of the driving member12, and the annular drums 44A of the driven member 14 are filled withthe MR fluid 16. Likewise, the annular spaces between the annular drums24B of the driving member 12, and the annular drums 44B of the drivenmember 14 are filled with the MR fluid 16. However, the respectiveannular spaces (fluid chambers) are separated from one another, i.e.,the MR fluid 16 may not flow from one of the annular space to the other.According to an embodiment, the annular spaces have a width of 0.25 mm+/−0.05 mm, between the facing surfaces of sets of drums 24A and 24B,i.e., in the radial direction. The annular spaces width range isprovided only as a non-exclusive example, as other annular spaces widthsare considered as well, taking into account various factors such asoverall torque, part sizes, etc. The annular spaces between each set ofdrum 24 and 44 (i.e., one set of 24A and 44A, and the other set of 24Band 44B) are part of a MR fluid chamber sealed off by seals 31. The MRfluid clutch apparatus 10 has two MR fluid chambers, one for the drums24A/44A and another associated with the drums 24B/44B. Therefore, if theMR fluid leaks out of one of the chambers, the other chamber may stillbe functional, thereby adding a redundancy.

As best seen in FIGS. 2D and 2E, the output casing 40 defines expansionsystems for each of the MR fluid chambers, to compensate for pressurevariations. According to an embodiment, the expansion systems comprisesthroughbores 46 in the casing 40. The throughbores 46 are in fluidcommunication with the MR fluid chambers, for MR fluid to passtherethrough. Flexible membranes 47 are secured to an exterior of thecasing 40, opposite the throughbores 46, by way of brackets 48. Hence,the flexible membranes 47 may deform to create an expansion pocket. Theholes 26 defined in the annular flanges 23A and 23B allow the MR fluidto flow out of the annular spaces between the set of drums 24A/44A,24B/44B, to reach the expansion pockets. Fins 49 may also be provided onthe outer surface of the casing 40 to assist in exhausting heat from theMR fluid in the MR fluid chambers.

The MR fluid chambers include the annular spaces between the set ofdrums 24A/44A, 24B/44B, in addition to space at the end of drum tips,and space between the drums 24A and 24B and shear surfaces that are partof the casing 40 or core 80. The MR fluid chambers may also includespaces 60A and 60B, located opposite the annular flanges 23A and 23B.According to an embodiment, as shown in FIG. 2J, a flow MRFF of the MRfluid is as follows. When the driving member 12 rotates, the helicalchannels 25 create some pumping action, by which the MR fluid 16 movesin a radial outward direction after reaching ends of drums 24 and 44.Upon going beyond the outermost drums 24, the MR fluid may be directedpass the radial edge of the annular flanges 23 and into the spaces 60.The MR fluid will move radially inward, to return to the annular spacesvia the holes 26. The spaces 60 are in fluid communication with theexpansion systems.

The movement of the MR fluid in the manner described above allows the MRfluid to cycle in the MR fluid chambers. The movement is achieved viathe presence of the helical channels 25 on the surface of the drums 24.Other surface depressions could also be used on either one of the drums24/44 to induce a pumping action in the MR fluid chambers, i.e., someform of cavity, protrusion or channel in an otherwise smooth cylindricalsurface.

Referring to FIGS. 2H-2J, the electromagnet unit 18 is fixed to thedriven member 14 and therefore rotates with the driven member 14. Theelectromagnet unit 18 has a pair of electromagnets, 18A and 18B, sharinga core 80, although each of the electromagnets 18A and 18B could haveits own core. Annular coil 81A and 81B are in the core 80, and arerespectively part of the electromagnets 18A and 18B. The annular drums44A and associated annular support 45A are in line with theelectromagnet 18A and are secured to the core 80 and hence rotate withthe core 80. Likewise, the annular drums 44B and associated annularsupport 45B are in line with the electromagnet 18B and are secured tothe core 80 and hence rotate with the core 80. The core 80 has anH-shape section, with a base member 82 having a central web 83projecting radially to be sandwiched between the flanges 41A and 41B.Top members 84A and 84B complete the core 80. The top members 84A and84B are on either side of the central web 83, and are also sandwichedbetween the flanges 41A and 41B. Other arrangements are considered aswell, for instance the top members 84A and 84B being secured directly tothe central web 83, the use of a monolithic core as an alternative tothe embodiment shown, etc. As mentioned above, the annular supports 45Aand 45B are secured to the core 80, between the base member 82 and therespective top members 84A and 84B. In the illustrated embodiment, thecore 80 is part of the output casing 40 of the driven member 14, inaddition to being part of the electromagnet unit 18.

When a current passes through the annular coil 81A, a magnetic field isproduced in the appropriate side of the core 80 and through theintertwined arrangement of drums 24A and 44A and shear surfaces of thecasing 40/core 80, with MR fluid 16 therebetween. Likewise, when acurrent passes though the annular coil 81B, a magnetic field is producedin the appropriate side of the core 80, and through the intertwinedarrangement of drums 24B and 44B and shear surfaces of the casing40/core 80, with MR fluid 16 therebetween. Each coil 81A and 81B may beredundant: two coils in one for increased reliability, as observed fromFIGS. 2H and 2I. The magnetic fields may be produced separately (e.g.,one of the electromagnets 18A and 18B at a time) or concurrently, withthe same effect of causing a rotation of the core 80 and thus a rotationof the driven member 14. The magnetic field(s) therefore increase(s) theapparent viscosity of the MR fluid 16, to seize the drums 24A and 44Aand/or the drums 24B and 44B, to cause a transmission of the rotationalmotion from the drums 24A and/or 24B to the drums 44A and/or 44B. Theintertwined arrangement of drums 24A and 44A, and of drums 24B and 44B,allows the increase of the total clutch contact surface and of theclutch contact surface per volume of MR fluid 16. It is howeverconsidered to use a single drum 24A and a single drum 24B, to use theshear surfaces of the casing 40 (in the illustrated embodiment, theshear surfaces are part of the core 80) for transmission of force viathe MR fluid 16. Indeed, any appropriate configuration by which one ormore shear surfaces of the driving member 12 are separated from shearsurfaces of the driven member 14 by an annular space filled with MRfluid 16 is suitable.

In operation, according to one exemplary embodiment, a power source (notshown) causes the driving member 12 to rotate. MR fluid 16 transmits atleast some rotational energy (torque) to the driven member 14 by theapplication of a magnetic field by the electromagnet unit 18, therebycausing driven member 14 to rotate. The electromagnet unit 18 subjectsMR fluid 16 to a magnetic field that, if varied, may change the apparentviscosity of MR fluid 16. Changing the apparent viscosity of MR fluid16, in turn, may change the amount of rotational energy transferred fromdriving member 12 to driven member 14. Accordingly, in the example ofthe MR fluid clutch apparatus 10′, the amount of rotational energytransferred to driven member 14 may be regulated by controlling theamount of magnetic field generated by the electromagnet unit 18.

An example of magnetic field F is shown in greater detail in FIG. 2H,and is schematically illustrated as being created by both electromagnets18A and 18B. The clutch apparatus 10′ may have a high reliabilitybecause of coil and fluid chamber redundancy. Indeed, the duplication ofthe sets of drum (set 24A/44A and set 24B/44B), and associated annularspaces (a.k.a., fluid chamber) filled with MR fluid 16 is a redundancy,with the motion of the driving member 12 transmittable to the drivenmember 14 by actuation of a single side of the electromagnets 18A and18B. For example, in case of a coil failure as shown in FIG. 2I, themagnetic field generated by the coils may be on a single side of theelectromagnet, as shown as F′ as produced by electromagnet 18B. Thisunique feature may allow the clutch apparatus 10 to remain functionaldespite a coil failure. Likewise, leakage of the MR fluid 16 at one ofthe sides may not lead to failure of the clutch apparatus 10′, as theother side may remain operational to transmit the motion, due to theisolation of the two chambers of MR fluid 16. In the example of FIGS.2A-2F, the magnetic circuit low cross-section generation of and materialcomposition may minimize the Eddy currents and allow a high dynamicresponse.

The embodiment illustrated in FIGS. 2A-2J is that of one degree ofactuation (DOA) for one output degree of freedom (DOF), with one degreeof transmission redundancy provided by the MR fluid clutch apparatus10′. The embodiment shows an axial DOA (i.e., the driving member 12receives power from an axially connected shaft) to an axial output DOF(an output shaft is to be connected to the driven member 14. However,the axial output DOF could readily be converted to an output DOFincorporating a radial connector, similar to the configuration shown inFIG. 3.

Referring to FIG. 3, another embodiment of MR fluid clutch apparatus isshown as 10″, and is also known as single MR fluid actuator. The MRfluid clutch apparatus 10″ is similar to the MR fluid clutch apparatus10′ of FIGS. 2A-2F, whereby like components will bear like referencenumerals. However, the MR fluid clutch apparatus 10″ is configured toreceive a driving input from two independent sources, namely the drivingmember 12 (as in FIG. 2A-2F), and the driving member 112. For example,the driving member 12 may provide a rotational input in a firstorientation (e.g., clockwise), while the driving member 112 may providea rotational input in the opposite orientation. Alternatively, thedriving member 112 may provide a rotational input in the sameorientation for a redundant power input, or may be a stator to providesome form of braking input.

In the MR fluid clutch apparatus 10″, driven member 114 includes outputcasing 140, supported by bearings 30 so as to be rotatable about theaxis CL as journaled by the driving members 12 and 112. The casing hasthe first annular half 40A and the second annular half 40B, with aflange or connector 141 projecting radially from the halves 40A and 40B.The output of the driven member 114 is provided through the connector141, although other arrangements are possible as well. Hence, theconnector 141 has bores 142, to connect the connector 141 to otherequipment, components, linkages, etc.

Accordingly, the MR fluid clutch apparatus 10″ is configured to have thedriving members 12 and 112 share the core 80, although each of theelectromagnets 18A and 18B could have their own cores. In FIG. 3, theelectromagnet 18A produces a magnetic field F_(A) that causestransmission of rotation from the driving member 12 to the driven member114. The electromagnet 18B produces a magnetic field F_(B) that causestransmission of rotation from the driving member 112 to the drivenmember 114. If either one of the driving members 12 and 112 is a stator,the related magnet field F would block movement of the driven member 14.In yet another example of FIG. 3, the magnetic field F_(A) and F_(B)could cause rotations in different orientations of the driven member 14(clockwise and counterclockwise). It is pointed out that the controlleroperating the electromagnet unit 18 is programmed to avoid operating theelectromagnets 18A and 18B in such a way that conflicting actuation isperformed on the MR fluid clutch apparatus 10″, and safety features maybe provided to avoid damaging the MR fluid clutch apparatus 10″.

The embodiment illustrated in FIG. 3 is that of two DOAs for one outputDOF (clockwise output and counterclockwise output, or a redundant outputof same orientation). The stator may be regarded as providing a DOA asit provides braking power.

The MR fluid clutch apparatuses such as those illustrated as 10, 10′ and10″ in the preceding figures may be incorporated into a variety ofdifferent systems. For example, FIGS. 4A and 4B show acontrolled-slippage actuation (CSA) system 200 according to one exampleembodiment. By controlled slippage, reference is made to the variationin apparent viscosity that can be achieved by controlling the magneticfield to which is exposed the MR fluid. Although not illustrated,controllers are connected to the electromagnets of the variousembodiments having MR fluid clutch apparatuses as described herein, thecontrollers controlling the current sent to the electromagnets as aresponse to the transmission tasks required. For example, thecontrollers may be programmed with operation modules based on theintended use of the MR fluid clutch apparatuses in the CSAs.

FIG. 4A shows a schematic top view of CSA system 200, while FIG. 4Bshows a perspective view of CSA system 200. The CSA system 200 mayprovide two control outputs, although additional control outputs couldbe produced by the addition of clutch apparatuses.

In the example of FIGS. 4A and 4B, the CSA system 200 features fourrotary units defined by motors 201A and 201B, right-angle gearboxes 202(or straight gear boxes for parallel motor orientation instead of thetransverse orientation illustrated), unidirectional clutches 203, aclockwise-rotating shaft (CW shaft) 204A driven by either or both motors201A, and a counterclockwise-rotating shaft (CCW shaft) 204B driven byeither or both motors 201B. In the example of FIGS. 4A and 4B, motors201A and 201B may rotate CW shaft 204A and CCW shaft 204B atsubstantially constant speeds but in opposite directions. In the exampleembodiment of FIGS. 4A-4B, motors 201 are high-speed electric motors,although other power sources may be included, such as hydraulic motors.In this example embodiment, unidirectional clutches 203 are provided todisconnect jammed motors 201/gearboxes 202 from CW shaft 204A and CCWshaft 204B. In the event of a jammed rotary unit, the unidirectionalclutches 203 may be overrun by the redundant rotary unit, e.g., theother of the two motors 201A and gearboxes 202.

The CSA system 200 also has two pairs of MR fluid clutch apparatuses ofthe type shown as 10′ in FIGS. 2A-2F, and labelled as 205A and 205B fora first pair, and 206A and 206B for a second pair, and two outputlinkage assemblies 205C and 206C, respectively coupled to the 205A/205Bpair and the 206A/206B pair. Each pair of MR fluid clutch apparatusincludes one MR fluid clutch apparatus coupled to CW shaft 204A and oneMR fluid clutch apparatus coupled to CCW shaft 204B. Hence, a pair oftwo MR fluid clutch apparatuses receiving counterrotating inputs mayallow the pair, in combination, to control the back and forth motion oftheir respective output linkage assemblies 205C and 206C, the back andforth motion being illustrated by X1 and X2, respectively. The outputlinkage assemblies 205C and 206C are four-bar mechanism, each featuringa summing bar 207 receiving mechanical inputs from two input bars 208and 209 through appropriate rotational joints, the input bars 208 and209 being the driven member of the clutch apparatuses. Hence, the inputbars 208 and 209 cause output bar 210 to move in response. The outputbar 210 is connected to a component, a system, an assembly, etc, thatreceives the motion transmitted by the output bar 210. The output bars210 may be connected to different components, to a same component, etc.

In operation, according to the embodiment on FIGS. 4A and 4B, CW shaft204A and CCW shaft 204B rotate in opposite directions. Each of the MRfluid clutch apparatuses 205A, 205B, 206A and 206B may transmit torqueto its associated output linkage assembly (205C or 206C) in therotational orientation of the driving shaft (204A or 204B), by varyingthe apparent viscosity of the MR fluid within the MR fluid clutchapparatus, for example, in the manner described in FIGS. 2A-2F ofvarying the electrical current provided in the coil of the electromagnet18A and/or 18B). Hence, each of the 205A/205B pair and the 206A/206Bpair is capable of producing force to its output linkage assembly (205Cor 206C) in both directions. For example, providing a substantiallylarger amount of electrical current to the electromagnet of MR fluidclutch apparatus 206A than to the electromagnet of MR fluid clutchapparatus 206B may transmit torque at the output bar 210 in theclockwise direction at its junction with the input bar 209. Inversely,providing a substantially larger amount of electrical current to theelectromagnet of MR fluid clutch apparatus 206B than to theelectromagnet of MR fluid clutch apparatus 206A may transmit torque atthe output bar 210 in the counter-clockwise direction at its junctionwith the input bar 209. In this manner, CSA system 200 may transmitcontrol outputs provided through each output linkage assembly bychanging the current provided to each MR fluid clutch apparatus.

The CSA system 200 may result in a reduction of maintenance operationsand environmental impact, when used as an alternative to traditionalhydraulic actuators performing the same movements at the same torqueorder of magnitude. Furthermore, the CSA system 200 may satisfyreliability standards by providing redundant components (e.g., multiplemotors 201, gearboxes 202, component redundancy within each MR fluidclutch apparatus such as the pair of electromagnets 18A and 18B).Moreover, the MR fluid clutch apparatuses described herein haverelatively few components, relatively few moving parts, and transfertorque through fluid rather than solid contact surfaces. In addition,the CSA system 200 may provide higher dynamic response than hydraulicand electromechanical actuators through inertia decoupling by the MRfluid clutch apparatuses and by the fast response time.

The embodiment illustrated in FIGS. 4A and 4B provides four DOAs for twooutput DOF with two degrees of actuation redundancy, or two DOAs (whentwo motors are present) and the two output DOFs (twoclockwise/counterclockwise output DOFs). It is even considered toprovide four DOAs for one output DOF if the output bars 210 areinterconnected, the system having three degrees of actuation redundancy.However, additional assemblies pairs of MR fluid clutch apparatusescould be added for supplemental output DOFs. Moreover, it is considerednot to provide the two degrees of actuation redundancy, for example byhaving two motors instead of four, with each motor having two shaft endsto create the arrangement shown in FIGS. 4A-4B. Moreover, the combinedpower of paired motors 201A may be used to concurrently drive shaft204A, and the combined power of paired motors 201 B may be used toconcurrently drive shaft 204B. This may enable the use of smallermotors.

As an alternative to the concept taught by the CSA system 200 employingmultiple shafts, CSA system 300 of FIG. 5 considers providingbidirectional control with a single shaft. The CSA system 300 features amotor 301, a shaft 302, and three pairs of MR fluid clutch apparatuses303A/B, 304A/B, 305A/B. Each pair of MR fluid clutch apparatuses isassociated to a respective output linkage assembly 303C, 304C, 305C in abell crank arrangement. Each pair comprises two MR fluid clutchapparatus, for example having a similar configuration to the MR fluidclutch apparatus 10 of FIG. 2A. Each MR fluid clutch apparatus has adedicated output lever 306, with each of the pairs 303A/B, 304A/B,305A/B having one lever pivot point above the longitudinal axis of thedriving shaft 302 (see 306A), and the other lever pivot point below thelongitudinal axis of the driving shaft 302 (see 306B). In this manner,torque transmitted in the clockwise direction by MR fluid clutchapparatus 303A results in torque in the clockwise direction at theoutput pivot point 307A of the linkage assembly 303C, whereas torquetransmitted in the clockwise direction by MR fluid clutch apparatus 303Bresults in torque in the counter-clockwise direction at the output pivotpoint 307A. Hence, with a single shaft 302, the CSA 300 produces areciprocating output movement for its output linkage assemblies 303C,304C, 305C.

The embodiment illustrated in FIG. 5 is highly underactuated, with oneDOA for, three output DOFs, via six degrees of transmission (six clutchapparatuses). The embodiment of FIG. 5 could have more or less outputDOAs and DOFs.

In accordance to yet another embodiment illustrative of a potential useof the MR fluid clutch apparatuses of the present disclosure, FIG. 6shows a clutch-redundant rotary motor (CRRM) system 400. The CRRM system400 provides a mechanical output through linkage 401. In this exampleembodiment, the CRRM system 400 has rotary units 402A and 402B. Therotary units 402A and 402B have respective motors 403A and 403B,gearboxes 404A and 404B, and MR fluid clutch apparatus 405A and 405B,the MR fluid clutch apparatuses being similar in operation to the MRfluid clutch apparatus 10 of FIG. 2A, with redundant electromagnets.

In operation, according to one embodiment, motors 403A and/or 403B mayprovide mechanical energy to displace linkage 401. If, in one examplescenario, motor 403A jams or otherwise fails to work properly, clutch405A may disengage motor 403A and allow motor 403B to drive movement oflinkage 401. The clutch 405A is disengaged by a change in the magneticfield provided to its MR fluid to create a decrease in apparentviscosity. In the example of FIG. 6, two motors are provided in the CRRMsystem 400 to provide a redundant motor. It is considered to provide aplurality of the CRRM systems 400 together to provide redundancy to amulti-output system.

The embodiment illustrated in FIG. 6 shows two DOAs for one output DOFwith one degree of actuation redundancy. This may include an embodimentin which the motors 403A and 403B are both directional. Alternatively,the DOAs may provide opposite orientations.

Referring to FIG. 7, in accordance to yet another embodimentillustrative of a potential use of the MR fluid clutch apparatuses ofthe present disclosure, a CRRM system 500 is illustrated. The CRRMsystem 500 features two primary rotary units 501A and 501B, a sharedrotary unit 501C; and linkages 502A and 502B. Each of the primary rotaryunits 501A/501B may include a single motor 503A/503B, gearbox 504A/504B,and MR fluid clutch apparatus 505A/505B. Shared rotary unit 501C alsofeatures a single motor 503C, a gearbox 504C, but an MR fluid clutchapparatus 505C for each of rotary units 501A and 501B. The MR fluidclutch apparatus 505C are on a drive shaft 506 driven by the singlemotor 503C via gearbox 504C. Linkage 502A couples the rotary unit 501Ato the shared rotary unit 501C, whereas linkage 502B couples the rotaryunit 501 B to the shared rotary unit 501C.

In operation, according to an embodiment, the rotary unit 501A may drivelinkage 502A, and the rotary unit 501B may drive linkage 502B. Therotary unit 501C may remain disengaged so long as rotary units 501A and501B are operating properly. If, however, a failure occurs (e.g., the MRfluid clutch apparatus 505A or the gearbox 504A fails or the motor503A), the MR fluid clutch apparatus 505A of rotary unit 501A may bedisengaged, and the MR fluid clutch apparatus 505C may engage sharedrotary unit 501C so as to allow shared rotary unit 501C to drive linkage502A.

In this manner, the shared rotary unit 501C may be sufficient to provideredundancy to all two primary rotary units 501A and 501B in the eventthat one primary rotary unit fails. It is contemplated to extend theconfiguration of the CRRM system 500 to more than two primary rotaryunits, by sharing multiple rotary units with the shared rotary unit501C.

Hence, in FIG. 7, the configuration shows DOAs for two output DOFs withone shared degree of actuation redundancy. The degree of actuationredundancy could be shared between more than two DOAs by adding rotaryunits.

What is claimed is:
 1. A magnetorheological fluid clutch apparatuscomprising: at least one input rotor adapted to be coupled to a powerinput, the input rotor having a first set of at least one input shearsurface, and a second set of at least one input shear surface, the firstset and the second of the input rotor rotating concurrently in a sameorientation; an output rotor rotatably mounted about the input rotor forrotating about a common axis with the input rotor, the output rotorhaving a first set of at least one output shear surface, and a secondset of at least one output shear surface, the first sets of the inputrotor and the output rotor separated by at least a first annular spaceand forming a first transmission set, the second sets of the input rotorand the output rotor separated by at least a second annular space andforming a second transmission set; magnetorheological fluid in each ofthe annular spaces, the MR fluid configured to generate a variableamount of torque transmission between the sets of input rotor and outputrotor when subjected to a magnetic field; and a pair of electromagnets,with a first electromagnet associated with the first transmission set,and a second electromagnet associated with the second transmission set,the electromagnets configured to deliver a magnetic field through the MRfluid, the electromagnets configured to vary the strength of themagnetic field; whereby actuation of at least one of the pair ofelectromagnets results in torque transmission from the at least oneinput rotor to the output rotor.
 2. The magnetorheological fluid clutchapparatus according to claim 1, wherein each of the first set of inputshear surface and the second set of input shear surface are part offirst input drums and second input drums, and further wherein at leastone of each of the output shear surfaces are part of first output drumsand second output drums, the input and output shear surfaces of each ofthe transmission sets being intertwined.
 3. The magnetorheological fluidclutch apparatus according to claim 1, wherein the at least firstannular space is part of a first magnetorheological fluid chamber, andfurther wherein the at least second annular space is part of a secondmagnetorheological fluid chamber.
 4. The magnetorheological fluid clutchapparatus according to claim 3, wherein each of the magnetorheologicalfluid chambers has an expansion system.
 5. The magnetorheological fluidclutch apparatus according to claim 4, wherein the expansion systemcomprises at least one flexible member on an exterior of the outputrotor forming an expansion pocket in fluid communication with one of themagnetorheological fluid chambers.
 6. The magnetorheological fluidclutch apparatus according to claim 1, wherein each of theelectromagnets comprises at least two independent coils.
 7. Themagnetorheological fluid clutch apparatus according to claim 2, whereinat least one of the first and second input drums and the first andsecond output drums has a helical channel in at least one of itssurfaces facing a respective one of the first annular space and secondannular space, the respective one of the first annular space and secondannular space being in fluid communication with a fluid chamber space,whereby the helical channel induces a flow of the magnetorheologicalfluid between the respective one of the first annular space and secondannular space and the fluid chamber space when the input rotor rotates.8. The magnetorheological fluid clutch apparatus according to claim 7,wherein the fluid chamber space is separated from the respective one ofthe first annular space and second annular space by at least one hole ina radial wall of the input drums.
 9. The magnetorheological fluid clutchapparatus according to claim 1, wherein the at least one input rotorcomprises two input rotors, with a first of the input rotors associatedwith the first transmission set and a second of the input rotorsassociated with the second transmission set.
 10. The magnetorheologicalfluid clutch apparatus according claim 9, wherein the first of the inputrotors receives a clockwise input, and further wherein the second of theinput rotors receives a counterclockwise input.
 11. Themagnetorheological fluid clutch apparatus according claim 9, wherein thefirst of the input rotors receives a rotating input, and further whereinthe second of the input rotors is fixed.
 12. The magnetorheologicalfluid clutch apparatus according to claim 1, wherein the pair ofelectromagnets share a common core, the common core being fixed to theoutput rotor.
 13. A magnetorheological fluid clutch apparatuscomprising: at least one input rotor adapted to be coupled to a powerinput, the input rotor having at least a first set of at least one inputdrum; an output rotor rotatably mounted about the input rotor forrotating about a common axis with the input rotor, the output rotorhaving at least a first set of at least one output shear surface, thefirst sets of the input rotor and the output rotor separated by at leasta first annular space and forming a first transmission set; a fluidchamber space being in fluid communication with the first annular space,at least one surface depression channel in a surface of one of the atleast one input drum and the at least one output shear surface facingthe annular space; magnetorheological fluid in the annular space, the MRfluid configured to generate a variable amount of torque transmissionbetween the sets of input rotor and output rotor when subjected to amagnetic field; and at least one electromagnet configured to deliver amagnetic field through the MR fluid, the at least one electromagnetconfigured to vary the strength of the magnetic field whereby actuationof the at least one electromagnet resulting in torque transmission fromthe at least one input rotor to the output rotor; whereby the surfacedepression induces a flow of the magnetorheological fluid between theannular space and the fluid chamber space when the input rotor rotates.14. The magnetorheological fluid clutch apparatus according to claim 13,wherein each of the first set of at least one input drums comprises aplurality of the input drums, and wherein at least one of the outputshear surfaces is part of a first output drum, the input drum and outputshear surfaces being intertwined.
 15. The magnetorheological fluidclutch apparatus according to claim 13, wherein the at least firstannular space is part of a first magnetorheological fluid chamber. 16.The magnetorheological fluid clutch apparatus according to claim 13,wherein an expansion system comprises at least one flexible member on anexterior of the output rotor forming an expansion pocket in fluidcommunication with the magnetorheological fluid chamber.
 17. Themagnetorheological fluid clutch apparatus according to claim 13, whereinthe at least one electromagnet comprises at least two independent coils.18. The magnetorheological fluid clutch apparatus according to claim 13,wherein the at least one input rotor receives an axial power input, andthe output rotor has one of an axially-positioned connector and a radialconnector for transmitting a power output.
 19. The magnetorheologicalfluid clutch apparatus according to claim 13, wherein the at least oneinput rotor comprises two input rotors, with a first of the input rotorsassociated with the first transmission set and a second of the inputrotors associated with a second transmission set.
 20. Themagnetorheological fluid clutch apparatus according to claim 13, whereinthe at least one surface depression is at least one helical channel.